1. Field of the Invention
The present invention relates to a floating cover for a liquid storage tank, and more particularly, to a liquid surface contact internal floating cover constructed with a plurality of floating panels and process for monitoring leaks within each of the floating panels.
2. Description of the Background Art
Floating covers have previously been used inside cylindrical liquid storage tanks to ride vertically along the cylindrical wall of the tanks between the roof and bottom as the volume of fluid held by the tank varies. Typically, the floating cover floats above the liquid and moves up and down depending on the amount of the liquid. A plurality of buoyant panels or honeycomb type pans, are assembled to form the floating cover. This conventional floating cover, however, is expensive to manufacture and erect inside the frame of the tank. Accordingly, periodic inspection and maintenance of the cover is desirable in order to obtain the full life of the cover.
The current design for full surface contact floating covers uses honeycomb panels that are manufactured by bonding an aluminum channel frame to the honeycomb panel. The honeycomb panel may have all sealed cells or all interconnected cells. If some of the cells of an individually sealed honeycomb are opened to invasion of the product held by the tank, there is currently no way of detecting the invasion except by observation of the escaped product as it drips out of the panel after the tank has been taken out of service and emptied. The trapped liquid will however, slowly drip out of the panel and present a grave safety hazard to the maintenance people working within the interior of the tank. If a cell of an interconnecting cell type of honeycomb panel is violated, then all cells are violated, making it near impossible to find the original leaking cell. The whole panel must be replaced.
The owners and managers of tanks must periodically inspect the interior of the tank and make repairs. This entails a removal of the contents of the tank, a purging of gaseous phase vapors from the interior of the tank, an introduction of ambient atmospheric air into the interior of the tank and continuous or at least intermittent monitoring of the atmosphere within the interior of the tank. The owner of the tank needs assurance that before personnel enter the interior of the empty tank, and that while work (particularly using arc or open flame torches) is performed within the interior of the tank, that the tank has been completely emptied and cleaned, and is safe for both the personnel and the type of work being performed. This assurance requires that there be no remaining hazardous pockets of the contents of the tank within the floating roof.
Currently, contemporary designers of buoyant panels provide no convenient technique for detecting the presence of moisture and condensate within individual buoyant panels.
It is an object of the present invention to provide an improved floating roof.
It is another object to provide a floating roof and process for detecting the presence of vapor, moisture, or condensate which indicates leakage and the onset of deterioration of the integrity of the roof.
It is still another object to provide a floating roof assembled from multiple panels and a process for inspecting individual panels for the onset of deterioration.
It is yet another object to provide a floating cover able to remove and replace individual floating panels of a frame for the floating cover without interfering with the integrity of adjacent floating panels.
It is still yet another object to provide a floating cover that permits inspection of leakage of each of the floating panels forming the floating cover without disassembly of the floating cover.
It is a further object to provide a full liquid surface contact internal floating cover constructed with individual floatation panels that may be checked for leakage from the top side of the cover while the tank is in service.
It is still another object to provide a full liquid surface contact internal floating cover that accommodates vapor sampling of the entire interior volume of the floatation panels.
It is yet a further object to provide a full liquid surface contact internal floating cover assembled from floatation panels set into the frame of the cover from the top side of the floating roof.
It is a still yet further object to provide a full liquid surface contact internal floating cover assembled from a plurality of floatation panels, with adjacent panels allowing unrestricted removal of individual floatation panels.
It is also an object to provide a full liquid surface contact internal floating cover with a frame for support of discrete floatation panels that is constructed from rigid structural members.
It is also an object to provide a full liquid surface contact internal floating cover constructed from a plurality of floatation panels that are not relied upon for the structural rigidity of the cover and therefore are not subjected to failure due to metal fatigue.
It is also an object to provide a full liquid surface contact internal floating cover constructed from a plurality of floatation panels that may be leak tested at the point of manufacture as well as in the field after assembly of the cover.
It is also object to provide a floating cover that allows individual panels within the floating cover to be inspected without detaching either the particular panel being inspected or any adjacent panel from the floating cover.
These and other objects may be achieved by providing a storage tank with a floating cover including a frame having a plurality of openings, a plurality of floating panels mounted into the respective openings in the frame, an inspection port formed on an upper member of each of the floating panels that when opened, communicates with an hollow cavity interior of the floating panel, and a cap covering the inspection port of the floating panel. The presence of moisture and condensate contained in any of floating panels can be visually detected through the inspection port of the each of the floating panels without disassembling any of the floating panels or without removing the entire floating cover from the storage tank.